1. CHAPTER 3 INPUT/OUTPUT

2. In this chapter, you will:  Learn what a stream is and examine input and output streams  Explore how to read data from the standard input device  Learn how to use predefined functions in a program  Explore how to use the input stream functions get, ignore, fill, putback, and peek  Become familiar with input failure  Learn how to write data to the standard output device  Discover how to use manipulators in a program to format output  Learn how to perform input and output operations with the string data type  Become familiar with file input and output

3. Input/Output Streams I/O is a sequence of bytes, called a stream of bytes, from the source to the destination. The bytes are usually characters, unless the program requires other types of information such as a graphic image or digital speech. A stream is a sequence of characters from the source to the destination. Input Stream: A sequence of characters from an input device to the computer. Output Stream: A sequence of characters from the computer to an output device.

4. I/O STREAMS AND STANDARD I/O DEVICES  To extract (that is, receive) data from keyboard and send output to the screen, every C++ program must use the header file iostream.  This header file, iostream, contains definitions of two data types, istream (input stream) and ostream (output stream).  The header file, iostream, contains the declaration of two variables, cin (stands for common input), pronounced see-in, and cout (stands for common output), pronounced see-out, and the declaration is similar to the following C++ statements: istream cin; ostream cout;  To use cin and cout every C++ program must use the preprocessor directive #include

5.  Variables of the type istream are called input stream variables.  Variables of the type ostream are called output stream variables.  A stream variable is either an input stream variable or an output stream variable.

6. cin and the Extraction Operator ( >>) Consider the following C++ statement: cin>>payRate; If you type 15.50, the value stored in payRate after the execution of this statement is 15.50.  The extraction operator >> is binary. The left-hand operand is an input stream variable such as cin. The right-hand operand is a variable of a simple data type.  The purpose of an input statement is to read and store values in a memory location and only variables refer to memory locations, the items (that is, right hand operand in the case of the extraction operator, >> ) must be a variable in an input statement.

7. The syntax of an input statement using cin and the extraction operator >> is cin>>variable>>variable...;

8.  Every occurrence of >> extracts the next data item from the input stream.  You can read both payRate and hoursWorked via a single cin statement by using the following code: cin>>payRate>>hoursWorked;  There is no difference between the preceding cin statement and the following two cin statements. cin>>payRate; cin>>hoursWorked;  When scanning for the next input, >> skips all whitespaces.  Whitespace characters consist of blanks and certain nonprintable characters, such as tabs and the newline character.

9. Whether the input is 15.50 48.30 or 15.50 48.30 or 15.50 48.30 The input statement: cin>>payRate>>hoursWorked; would store 15.50 in payRate and 48.30 in hoursWorked.

10.  Suppose the input is 2. How does >> distinguish between character 2 and the number 2 ?  This is distinguished by the right hand operand of >>.  If the right hand operand, that is, variable, is of type char, input 2 is treated as character 2 (recall that in this case, the ASCII value of 2 will be stored). And if the right-hand operand is of the type int (or double ), input 2 is treated as the number 2.  Now consider the input 25 and the statement: cin>>a; where a is a variable of some simple data type.  If a is of the data type char, then only the single character 2 will be stored in a.  If a is of the data type, say int, then 25 will be stored in a.  If a is of the type double, then the input 25 is converted to a decimal number with zero decimal part.

11. Consider the statement cin>>a; where a is a variable of some simple data type.

12.  When reading data into a char variable, after skipping any leading whitespace characters, the extraction operator >> finds and stores only the next character; reading stops after a single character.  To read data into an int or double variable, after skipping all leading whitespace characters and reading the plus or minus sign (if any), the extraction operator >> reads the digits of the number, including the decimal point for floating-point variables, and stops when it finds a whitespace character or a character other than a digit.

13. Example 3-1 int a,b; double z; char ch,ch1,ch2; StatementInputValue Stored in Memory 1cin>>ch;Ach='A' 2cin>>ch;ABch='A', 'B' is held for later input 3cin>>a;48a=48 4cin>>a;46.35a=46,.35 is held for later input 5cin>>z;74.35z=74.35 6cin>>z;39z=39.0 7cin>>z>>a;65.78 38z=65.78, a=38 8cin>>a>>b;4 60a=4, b=60 9cin>>a>>ch>>z;57 A 26.9a=57, ch='A', z=26.9

14. 10cin>>a>>ch>>z;57 A 26.9a=57, ch='A', z=26.9 11cin>>a>>ch>>z;57 A 26.9a=57, ch='A', z=26.9 12cin>>a>>ch>>z;57A26.9a=57, ch='A', z=26.9 13cin>>z>>ch>>a;36.78B34z=36.78, ch='B', a=34 14cin>>z>>ch>>a;36.78 B34z=36.78, ch='B', a=34 15cin>>a>>b>>z;11 34a=11, b=34, Computer waits for the next number

15. 16cin>>a>>z;46 32.4 68a=46, z=32.4, 68 is held for later input 17cin>>ch>>a; 256ch='2', a=56 18cin>>a>>ch;256a=256, computer waits for the input value for ch. 19cin>>ch1>>ch2;A Bch1 = 'A', ch2 = 'B’ During program execution, when entering character data such as letters, you do not enter the single quotes around the character. Entering a char value into an int or double variable causes serious errors, called input failure.

16. USING PREDEFINED FUNCTIONS IN A PROGRAM A function, also called subprogram, is a set of instructions. When a function is activated, that is, executed, it accomplishes something. The function main is executed automatically when we execute a program. Other functions are executed only when they are called. The programming language C++ comes with a wealth of functions.

17. Predefined functions are organized as a collection of libraries, called header files. A particular header file may contain several functions. To use a particular function, you need to know the name of the function and a few other things. A very useful function, pow, called the power function, can be used to calculate x y in a program. That is, pow(x,y) = x y. pow(2,3)= 2 3 = 8 and pow(4,0.5) = 4 0.5 = 2. The numbers x and y that you use in the function pow are called the arguments or parameters of the function pow. In pow(2,3), the parameters are 2 and 3. An expression such as pow(2,3) is called a function call. The header file cmath contains the specification of the function pow.

18.  To use a predefined function in a program, you need to know the name of the header file containing the specification of the function and include that header file in the program.  In addition, you need to know the name of the function, the number of parameters the function takes, and the type of each parameter. You must also be aware of what the function is going to do.  To use the function pow, you must include the header file cmath.  The function pow has two parameters, both of which are numbers. The function calculates the first parameter to the power of the second parameter.

19. cin and the get Function Consider the declaration: char ch1, ch2; int num; and the input A 25 Now consider the statement: cin>>ch1>>ch2>>num; When the computer executes this statement, A is stored in ch1, blank is skipped by >>, 2 is stored in ch2, and 5 is stored in num. If we intended to store A in ch1, blank in ch2 and 25 in num ? It is clear that we can not use the extraction operator >>.

20.  The get function inputs the very next character (including whitespaces) from the input stream and stores in the memory location indicated by its argument.  The syntax of cin together with the get function to read a character is: cin.get(varChar); where varChar is a char variable.  varChar is called the argument or parameter of the function.  The next input character is stored in varChar.

21. Now, again, consider the input A 25 We can effectively use the get function as follows: cin.get(ch1); cin.get(ch2); cin>>num; to store A in ch1, blank in ch2, and 25 in num. The above set of statements is equivalent to the following: cin>>ch1; cin.get(ch2); cin>>num;

22. cin and the ignore Function  To process partial data, say with in a line, we can effectively use the ignore function to discard some portion of the input.  The syntax to use the function ignore is: cin.ignore(intExp,chExp); where intExp is an integer expression yielding an integer value and chExp is a char expression.  Suppose intExp yields a value, say m. This statement says, ignore the next m characters or until the character specified by chExp, whichever comes first.

23. Consider the following statement: cin.ignore(100,'\n'); The execution of this statement will ignore the next 100 characters or until the newline character is found whichever comes first. The execution of the statement: cin.ignore(100,'A'); will result in ignoring the first 100 characters or until the character 'A' is found, whichever comes first.

24. Example 3-2 int a,b; Suppose the input is: 25 67 89 43 72 12 78 34 Consider the statements: cin>>a; cin.ignore(100,'\n'); cin>>b; The first statement cin>>a; stores 25 in a. The second statement, cin.ignore(100,'\n'); discards all of the remaining numbers in the first line. The third statement cin>>b; stores 12 (from the next line) in b.

25. Example 3-3 char ch1,ch2; Suppose the input is Hello there. My name is Mickey. Now consider the statements: cin>>ch1; cin.ignore(100,'.'); cin>>ch2; The first statement cin>>ch1; stores 'H' in ch1. The second statement, cin.ignore(100,'.' ); results in ignoring all characters until '.' (period). The third statement cin>>ch2; stores 'M' (from the same line) in ch2.

26. The peek and the putback Functions  The putback function places the previous character extracted by the get function from an input stream back to that stream.  The peek function returns the next character from the input stream but it does not remove the character from that stream, that is, the next input character would be the same.  The syntax to use the function putback is: istreamVar.putback(ch); where istreamVar is an input stream variable, such as cin, and ch is a char variable.  The syntax to use the function peek is: ch = istreamVar.peek(); where istreamVar is an input stream variable, such as cin, and ch is a char variable.

27. Example 3-4 //Functions peek and putback #include using namespace std; int main() { char ch; cout<<"Line 1: Enter a string: ";//Line 1 cin.get(ch);//Line 2 cout<<endl;//Line 3 cout<<"Line 4: After first cin.get(ch); " <<"ch = "<<ch<<endl;//Line 4

28. cin.get(ch);//Line 5 cout<<"Line 6: After second cin.get(ch); " <<"ch = "<<ch<<endl;//Line 6 cin.putback(ch);//Line 7 cin.get(ch);//Line 8 cout<<"Line 9: After putback and then " <<"cin.get(ch); ch = "<<ch<<endl;//Line 9 ch = cin.peek();//Line 10 cout<<"Line 11: After cin.peek(); ch = " <<ch<<endl;//Line 11

29. cin.get(ch);//Line 12 cout<<"Line 13: After cin.get(ch); ch = " <<ch<<endl;//Line 13 return 0; } Sample Run: In this sample run, the user input is in red. Line 1: Enter a string: abcd Line 4: After first cin.get(ch); ch = a Line 6: After second cin.get(ch); ch = b Line 9: After putback and then cin.get(ch); ch = b Line 11: After cin.peek(); ch = c Line 13: After cin.get(ch); ch = c

30. The Dot Notation Between I/O Stream Variables and I/O Functions: A Precaution To use the get function we used statements such as cin.get(ch); Missing dot will result in compile time error. For example, in the statement cin.get(ch); cin and get are two separate identifiers, while in the statement cinget(ch); cinget becomes a new identifier and the compiler might be trying to resolve the problem of an undeclared identifier in the program. Similarly, missing parentheses will result in compile time error.

31. Several functions are associated with an istream variable, each doing a specific job. The functions get, ignore, and so on are members of the data type istream. Called the dot notation, the dot separates the input stream variable name from the member, or function, name. In C++, the dot is an operator called the member access operator. C++ has a special name for the data types istream and ostream. The data types istream and ostream are called classes. The variables cin and cout also have special names, called objects. cin is called an istream object cout is called an ostream object. Stream variables are called stream objects.

32. INPUT FAILURE Many things can go wrong during program execution. A program that is syntactically correct might produce incorrect results. Suppose that a part-time employee’s paycheck is calculated by using the following formula: wages = payRate * hoursWorked; If you accidentally type + in place of *, the calculated wages would be incorrect, even though the statement containing a + is syntactically correct.

33. What about an attempt to read invalid data? What would happen if you tried to input a letter into an int variable? If the input data did not match the corresponding variables, the program would run into problems. Trying to read a letter into an int or double variable would result in an input failure.

34. Consider the following statements int a, b, c; double x; If the input is W 54 then the statement cin>>a>>b; would result in an input failure because you are trying to input the character 'W' into the int variable a.

35. If the input is 35 67.93 48 78 then the input statement cin>>a>>x>>b; would result in storing 35 in a, 67.93 in x, and 48 in b. Now consider the following read statement with the previous input (the input with three values): cin>>a>>b>>c; This statement stores 35 in a and 67 in b. The reading stops at. (the decimal point). Because the next variable c is of the data type int, the computer tries to read. into c, which is an error. The input stream then enters a state called the fail state.

36. What actually happens when the input stream enters the fail state? Once an input stream enters a fail state, all further I/O statements using that stream are ignored. Unfortunately, the program quietly continues to execute with whatever values are stored in variables and produce incorrect results.

37. Example 3-5 //Input Failure program #include using namespace std; int main() { int a = 10; //Line 1 int b = 20; //Line 2 int c = 30; //Line 3 int d = 40; //Line 4 cout<<"Line 5: Enter four integers: "; //Line 5 cin>>a>>b>>c>>d; //Line 6 cout<<endl; //Line 7

38. cout<<"Line 8: The numbers you entered are:" <<endl; //Line 8 cout<<"Line 9: a = "<<a<<", b = "<<b <<", c = "<<c<<", d = "<<d<<endl; //Line 9 return 0; } Sample Run 1: The user input is in red. Line 5: Enter four integers: 34 K 67 28 Line 8: The numbers you entered are: Line 9: a = 34, b = 20, c = 30, d = 40

39. The clear Function When an input stream enters the fail state, the system ignores all further I/O using that stream. You can use the stream function clear to restore the input stream to a working state. The syntax to use the function clear is: istreamVar.clear(); Here istreamVar is an input stream variable, such as cin.

40. OUTPUT AND FORMATTING OUTPUT Syntax of cout when used together with the insertion operator << is cout<<expression or manipulator <<expression or manipulator...; expression is evaluated, its value is printed, and manipulator is used to format the output. The simplest manipulator that you have used so far is endl, which is used to move the cursor to the beginning of the next line.

41. setprecision The general form of setprecision is: setprecision(n) where n is the number of decimal places. The statement cout<<setprecision(2); will output all decimal numbers up to two decimal places until it is reset. To use the manipulator setprecision, the program must include the header file iomanip. #include

42. fixed To output floating-point numbers in a fixed decimal format, you use the manipulator fixed. The following statement sets the output of floating-point numbers in a fixed decimal format on the standard output device: cout<<fixed; After the preceding statement executes, all floating-point numbers are displayed in the fixed-decimal format until the manipulator fixed is disabled.

43. You can disable the manipulator fixed by using the stream member function unsetf. The following statement disables the manipulator fixed on the standard output device, you use: cout.unsetf(ios::fixed); After the manipulator fixed is disabled, the output of the floating- point numbers return to their default settings. The manipulator scientific is used to output floating-point numbers in scientific format.

44. showpoint If the decimal part of a decimal number is zero, then when you instruct the computer to output the decimal number in a fixed decimal format, the output may not show the decimal point and the decimal part. To force the output to show the decimal point and trailing zeros, you use the manipulator showpoint. The following statement sets the output of decimal numbers with a decimal point and trailing zeros on the standard input device: cout<<showpoint; The following statement sets the output of a floating-point number in a fixed decimal format with the decimal point and trailing zeros on the standard output device: cout<<fixed<<showpoint;

45. Example 3-7 //Example: setprecision, fixed, showpoint #include using namespace std; int main() { double x,y,z; x = 15.674;//Line 1 y = 235.73;//Line 2 z = 9525.9864;//Line 3 cout<<fixed<<showpoint;//Line 4

46. cout<<setprecision(2) <<"Line 5: setprecision(2)"<<endl;//Line 5 cout<<"Line 6: x = "<<x<<endl;//Line 6 cout<<"Line 7: y = "<<y<<endl;//Line 7 cout<<"Line 8: z = "<<z<<endl;//Line 8 cout<<setprecision(3) <<"Line 9: setprecision(3)"<<endl;//Line 9 cout<<"Line 10: x = "<<x<<endl;//Line 10 cout<<"Line 11: y = "<<y<<endl;//Line 11 cout<<"Line 12: z = "<<z<<endl;//Line 12

47. cout<<setprecision(4) <<"Line 13: setprecision(4)"<<endl;//Line 13 cout<<"Line 14: x = "<<x<<endl;//Line 14 cout<<"Line 15: y = "<<y<<endl;//Line 15 cout<<"Line 16: z = "<<z<<endl;//Line 16 cout<<"Line 17: " <<setprecision(3)<<x<<" " <<setprecision(2)<<y<<" " <<setprecision(4)<<z<<endl;//Line 17 return 0; }

48. Output: Line 5: setprecision(2) Line 6: x = 15.67 Line 7: y = 235.73 Line 8: z = 9525.99 Line 9: setprecision(3) Line 10: x = 15.674 Line 11: y = 235.730 Line 12: z = 9525.986 Line 13: setprecision(4) Line 14: x = 15.6740 Line 15: y = 235.7300 Line 16: z = 9525.9864 Line 17: 15.674 235.73 9525.9864

49. The stream function setf can be used to set fixed, scientific, and showpoint. In this case, fixed, scientific, and showpoint are referred to as ios::fixed, ios::scientific, and ios::showpoint, respectively, and are called formatting flags. Both the flags ios::fixed and ios::scientific are part of ios::floatfield, which is a data type in C++. When setting the fixed or scientific flag, to ensure that only either the ios::fixed or ios::scientific flag is set, you must pass ios::floatfield as a second argument to the function setf. cout.setf(ios::fixed,ios::floatfield);

50. The following statement sets the flag ios::showpoint to output floating-point numbers with a decimal point and trailing zeros on the standard output device: cout.setf(ios::showpoint);

51. C++ provides the manipulator setiosflags, to set the flags ios::fixed, ios::scientific, and ios::showpoint. To use the manipulator setiosflags, the program must include the header file iomanip. The following statement uses the manipulator setiosflags to set the flags ios::fixed and ios::showpoint on the standard output device: cout<<setiosflags(ios::fixed); cout<<setiosflags(ios::showpoint);

52. You can specify more than one flag in the manipulator setiosflags by separating the flags with the symbol |. The following statement sets both the flags ios::fixed and ios::showpoint on the standard output device: cout<<setiosflags(ios::fixed | ios::showpoint);

53. setw setw(n) - output the value of the next expression in n columns.  The output is right justified.  If the number of specified columns is less than the number of columns required by the output, then the output is automatically expanded to the required number of columns.  Unlike setprecision, which controls the output of all floating- point numbers until it is reset, setw controls the output of only the next expression.  To use the manipulator setw, the program must include the header file iomanip.

54. Example 3-8 //Example: setw #include using namespace std; int main() { int x = 19;//Line 1 int a = 345;//Line 2 double y = 76.384;//Line 3 cout<<fixed<<showpoint;//Line 4

55. cout<<"12345678901234567890"<<endl;//Line 5 cout<<setw(5)<<x<<endl;//Line 6 cout<<setw(5)<<a<<setw(5)<<"Hi" <<setw(5)<<x<<endl<<endl;//Line 7 cout<<setprecision(2);//Line 8 cout<<setw(6)<<a<<setw(6)<<y <<setw(6)<<x<<endl;//Line 9 cout<<setw(6)<<x<<setw(6)<<a <<setw(6)<<y<<endl<<endl;//Line 10 cout<<setw(5)<<a<<x<<endl;//Line 11 cout<<setw(2)<<a<<setw(4)<<x<<endl;//Line 12 return 0; }

56. Output: 12345678901234567890 19 345 Hi 19 345 76.38 19 19 345 76.38 34519

57. ADDITIONAL OUTPUT FORMATTING TOOLS fill and setfill In the manipulator setw if the number of columns specified are more than the number of columns required by the expression, the output of the expression is right justified and the unused columns to the left are filled with spaces. The output stream variables, such as cout, can use the function fill and/or the manipulator setfill to fill the unused columns with a character other than the space. The syntax to use the function fill is: ostreamVar.fill(ch); where ostreamVar is an output stream variable and ch is a character. For example, the statement cout.fill('*'); sets the filling character to '*' on the standard output screen.

58. The syntax to use the manipulator setfill is: ostreamVar<<setfill(ch); where ostreamVar is an output stream variable and ch is a character. The statement cout<<setfill('#'); sets the filling character to '#'.

59. Example 3.9 //Example: fill and setfill #include using namespace std; int main() { int x = 15;//Line 1 int y = 7634;//Line 2 cout<<"12345678901234567890"<<endl;//Line 3 cout<<setw(5)<<x<<setw(7)<<y <<setw(8)<<"Warm"<<endl;//Line 4 cout.fill('*');//Line 5 cout<<setw(5)<<x<<setw(7)<<y <<setw(8)<<"Warm"<<endl;//Line 6

60. cout<<setw(5)<<x<<setw(7)<<setfill('#') <<y<<setw(8)<<"Warm"<<endl;//Line 7 cout<<setw(5)<<setfill('@')<<x <<setw(7)<<setfill('#')<<y <<setw(8)<<setfill('^')<<"Warm" <<endl;//Line 8 cout.fill(' ');//Line 9 cout<<setw(5)<<x<<setw(7)<<y <<setw(8)<<"Warm"<<endl;//Line 10 return 0; } Output: 12345678901234567890 15 7634 Warm ***15***7634****Warm ***15###7634####Warm @@@15###7634^^^^Warm 15 7634 Warm

61. The left and right Manipulators To left-justify the output, you use the manipulator left. The syntax to set the manipulator left is ostreamVar<<left; where ostreamVar is an output stream variable. The following statement sets the output to be left-justified on the standard output device: cout<<left;

62. You can disable the manipulator left by using the stream function unsetf. The syntax to disable the manipulator left is ostreamVar.unsetf(ios::left); where ostreamVar is an output stream variable. Disabling the manipulator left returns the output to the settings of the default output format. The following statement disables the manipulator left on the standard output device: cout.unsetf(ios::left);

63. The syntax to set the manipulator right is ostreamVar<<right; where ostreamVar is an output stream variable. The following statement sets the output to be right-justified on the standard output device: cout<<right;

64. Example 3-10 //Example: left justification #include using namespace std; int main() { int x = 15;//Line 1 int y = 7634;//Line 2 cout<<left;//Line 3 cout<<"12345678901234567890"<<endl;//Line 4 cout<<setw(5)<<x<<setw(7)<<y <<setw(8)<<"Warm"<<endl;//Line 5 cout.fill('*');//Line 6

65. cout<<setw(5)<<x<<setw(7)<<y <<setw(8)<<"Warm"<<endl;//Line 7 cout<<setw(5)<<x<<setw(7)<<setfill('#')<<y <<setw(8)<<"Warm"<<endl;//Line 8 cout<<setw(5)<<setfill('@')<<x <<setw(7)<<setfill('#')<<y <<setw(8)<<setfill('^')<<"Warm"<<endl; //Line 9 cout.unsetf(ios::left);//Line 10 cout.fill(' ');//Line 11 cout<<setw(5)<<x<<setw(7)<<y <<setw(8)<<"Warm"<<endl;//Line 12 return 0; }

66. Output : 12345678901234567890 15 7634 Warm 15***7634***Warm**** 15***7634###Warm#### 15@@@7634###Warm^^^^ 15 7634 Warm

67. The flush Function Both the manipulator endl and the newline escape sequence \n position the cursor at the beginning of the next line on the output device. When a program sends output to an output device, the output first goes to the buffer in the computer. Whenever the buffer becomes full, the output is sent to the output device. As soon as the manipulator endl is encountered, the output from the buffer is sent to the output device immediately, even if the buffer is not full. The manipulator endl positions the cursor at the beginning of the next line on an output device and helps clear the buffer. It is quite possible that sometimes you may not see the entire output because when the program terminates, the buffer at that time may not be full.

68. In C++, you can use the function flush to clear the buffer, even if the buffer is not full. In contrast to the manipulator endl, the function flush does not move the cursor to the beginning of the next line. The syntax to use the flush function is: ostreamVar.flush(); where ostreamVar is an output stream variable, such as cout. Just like endl, the function flush can be used as a manipulator. In such a case, flush is used in an output statement without the parentheses. For example, the following statement sends the output from the buffer to the standard output device: cout<<flush;

69. Example 3-11 Consider the following statements in which num is an int variable: cout<<"Enter an integer: " ;//Line 1 cin>>num;//Line 2 cout<<endl;//Line 3 The statement at Line 1 outputs the following text: Enter an integer: After outputting this line, the cursor stays positioned after the colon. The output of the statement at Line 1 first goes to the buffer. If the buffer is not full, this line of text might not be displayed. You could put the manipulator endl at the end of the statement at Line 1. However, by doing so, after printing the line of text, the cursor is positioned at the beginning of the next line.

70. The user is prompted to enter the number in the following line Suppose that the statement at Line 1 is replaced by the following statement: cout<<"Enter an integer: "<<flush;//Line 1 In this case, the line of text, Enter an integer: is displayed on the standard output device even if the buffer is not full. Moreover, after outputting the line of text, the cursor stays positioned after the colon; the user will then enter the number after the colon.

71. To use stream functions such as get, ignore, fill, clear, and setf in a program, the program must include the header file iostream. There are two types of manipulators: those with parameters and those without parameters. Manipulators with parameters are called parameterized stream manipulators. Manipulators such as setprecision, setw, setfill, and setiosflags are parameterized. Manipulators such as endl, fixed, scientific, showpoint, and left are without parameters. Because flush can also be used as a manipulator without any arguments, flush is a manipulator without parameters, too.

72. To use a parameterized stream manipulator—that is, a stream manipulator with parameters—in a program, you must include the header file iomanip. Manipulators without parameters are part of the iostream header file and, therefore, do not require inclusion of the header file iomanip.

73. Input/Output and the string Type You can use an input stream variable, such as cin, and the extraction operator >> to read a string into a variable of the data type string. If the input is the string "Shelly", the following code stores this input into the string variable name : string name; // declaration cin>>name; // input statement The extraction operator skips any leading whitespace characters and that reading stops at a whitespace character. You cannot use the extraction operator to read strings that contain blanks.

74. If the input is Alice Wonderland the value of the variable name after the following statement executes is "Alice" : cin>>name; To read a string containing blanks, you can use the function getline. The syntax to use the function getline is getline(istreamVar, strVar); where istreamVar is an input stream variable and strVar is a variable of the type string. The reading is delimited by the newline character, '\n'.

75. The function getline reads until it reaches the end of the current line. The newline character is also read but not stored in the string variable. Consider the following statement: string myString; If the input is 29 characters, bbbbHello there. How are you? where b represents a blank, after the statement getline(cin,myString); the value of myString is myString = " Hello there. How are you?"

76. File Input/Output File: An area in secondary storage used to hold information. For file I/O, the following steps are necessary. 1. Include the header file fstream in the program. So the following statement is needed. #include 2. Declare file ( fstream ) variables. For example the statements: ifstream inData; ofstream outData; declare the variable inData for input and outData for output. That is, inData is an input (file) stream variable and outData is an output (file) stream variable.

77. 3. Open Files The general syntax for opening a file is fileStreamVariable.open(sourceName, fileOpeningMode); Here fileStreamVariable is a file stream variable, sourceName is the name of the input/output file, and fileOpeningMode specifies the mode in which the file is to be opened.

79. Suppose declaration of Step 2. Suppose that the input data is stored in a file called prog.dat on a floppy disk in drive A:. Save the output in a file called prog.out on a floppy disk in drive A:. The following statements associate inData with prog.dat and outData with prog.out. inData.open("A:prog.dat"); //open input file outData.open("A:prog.out"); //open output file

80. Step 4:  Use the (file) stream variable together with >> or << or with other functions for input/Output.  The syntax for using >> or << with file variables is exactly similar to the syntax of cin and cout.  The statement inData>>payRate; reads the data from the file prog.dat and stores it in the variable payRate  The statement outData<<"The pay check is: "<<pay<<endl; stores the output line, which is: The pay check is: 565.78, in the file prog.out. Here we are assuming that the pay was calculated as 565.78.

81.  Close File inData.close(); outData.close();

82. #include //Add additional header files you use using namespace std; int main() { //Declare file stream variables such as the following ifstream inData; ofstream outData;... //Open files inData.open("A:prog.dat"); //open input file outData.open("A:prog.out"); // open output file //Code for data manipulation //Close files inData.close(); outData.close(); return 0; }

83. PROGRAMMING EXAMPLE: MOVIE TICKET SALE AND DONATION TO CHARITY A movie in a local theater is in great demand. To help a local charity, the theater owner has decided to donate a portion of the gross amount generated from the movie to the charity. This example designs and implements a program that prompts the user to input the movie name, adult ticket price, child ticket price, number of adult tickets sold, number of child tickets sold, and percentage of the gross amount to be donated to the charity. The output of the program is as follows. -*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-* Movie Name:....................... Duckey Goes to Mars Number of Tickets Sold:........... 2650 Gross Amount:..................... $ 9150.00 Percentage of Gross Amount Donated: 10.00% Amount Donated:................... $ 915.00 Net Sale:......................... $ 8235.00

84. Input The input to the program consists of the movie name, adult ticket price, child ticket price, number of adult tickets sold, number of child tickets sold, and percentage of the gross amount to be donated to the charity. Output The output is as shown above.

85. Problem Analysis and Algorithm Design grossAmount = adultTicketPrice * noOfAdultTicketsSold + childTicketPrice * noOfChildTicketsSold; The formulas to calculate the amount donated and the net sale amount are given below. 1. Get the movie name. 2. Get the price of an adult ticket price. 3. Get the price of a child ticket price. 4. Get the number of adult tickets sold. 5. Get the number of child tickets sold. 6. Get the percentage of the gross amount donated to the charity.

86. 7. Calculate the gross amount using the following formula: grossAmount = adultTicketPrice * noOfAdultTicketsSold + childTicketPrice * noOfChildTicketsSold; 8. Calculate the amount donated to the charity using the following formula: amountDonated = grossAmount * percentDonation / 100; 9. Calculate the net sale amount using the following formula: netSale = grossAmount – amountDonated;

87. Variables string movieName; double adultTicketPrice; double childTicketPrice; int noOfAdultTicketsSold; int noOfChildTicketsSold; double percentDonation; double grossAmount; double amountDonated; double netSaleAmount;

88. Formatting Output In the output, the first column is left-justified and the numbers in the second column are right-justified. When printing a value in the first column, the manipulator left is used; before printing a value in the second column, the manipulator right is used. The empty space between the first and second columns is filled with dots; the program uses the manipulator setfill to accomplish this goal. In the lines showing the gross amount, amount donated, and net sale amount, the space between the $ sign and the number is filled with blank spaces. Before printing the dollar sign, the program uses the manipulator setfill to set the filling character to blank.

89. The following statements accomplish the desired output: cout<<"-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*" <<"-*-*-*-*-*-*-*-*-*-*-*-*-*"<<endl; cout<<setfill('.')<<left<<setw(35)<<"Movie Name: " <<right<<" "<<movieName<<endl; cout<<left<<setw(35)<<"Number of Tickets Sold: " <<setfill(' ')<<right<<setw(10) <<noOfAdultTicketsSold + noOfChildTicketsSold <<endl; cout<<setfill('.')<<left<<setw(35)<<"Gross Amount: " <<setfill(' ')<<right<<" $" <<setw(8)<<grossAmount<<endl; cout<<setfill('.')<<left<<setw(35) <<"Percentage of Gross Amount Donated: " <<setfill(' ')<<right <<setw(9)<<percentDonation<<'%'<<endl;

90. cout<<setfill('.')<<left<<setw(35)<<"Amount Donated: " <<setfill(' ')<<right<<" $" <<setw(8)<<amountDonated<<endl; cout<<setfill('.')<<left<<setw(35)<<"Net Sale: " <<setfill(' ')<<right<<" $" <<setw(8)<<netSaleAmount<<endl;

91. Main Algorithm 1. Declare the variables. 2. Set the output of the floating-point numbers to two decimal places in a fixed decimal format with a decimal point and trailing zeros. Therefore, you need to include the header file iomanip. 3. Prompt the user to enter a movie name. 4. Input (read) the movie name. Because the name of a movie might contain more than one word (and, therefore, might contain blanks), the program uses the function getline to input the movie name. Moreover, because the function getline also reads the newline character, after entering the movie name on a line, you need to press the Enter key twice. 5. Prompt the user to enter the price of an adult ticket. 6. Input (read) the price of an adult ticket. 7. Prompt the user to enter the price of a child ticket.

92. 8. Input (read) the price of a child ticket. 9. Prompt the user to enter the number of adult tickets sold. 10. Input (read) the number of adult tickets sold. 11. Prompt the user to enter the number of child tickets sold. 12. Input (read) the number of child tickets sold. 13. Prompt the user to enter the percentage of the gross amount donated. 14. Input (read) the percentage of the gross amount donated. 15. Calculate the gross amount. 16. Calculate the amount donated. 17. Calculate the net sale amount. 18. Output the results.

93. #include using namespace std; int main() { //Step 1 string movieName; double adultTicketPrice; double childTicketPrice; int noOfAdultTicketsSold; int noOfChildTicketsSold; double percentDonation; double grossAmount; double amountDonated; double netSaleAmount;

94. cout<<fixed<<showpoint<<setprecision(2); //Step 2 cout<<"Enter movie name: "<<flush; //Step 3 getline(cin,movieName); //Step 4 cout<<endl; cout<<"Enter the price of an adult ticket: "<<flush; //Step 5 cin>>adultTicketPrice;//Step 6 cout<<endl; cout<<"Enter the price of a child ticket: "<<flush; //Step 7 cin>>childTicketPrice;//Step 8 cout<<endl;

95. cout<<"Enter number of adult tickets sold: "<<flush; //Step 9 cin>>noOfAdultTicketsSold;//Step 10 cout<<endl; cout<<"Enter number of child tickets sold: "<<flush; //Step 11 cin>>noOfChildTicketsSold;//Step 12 cout<<endl; cout<<"Enter the percentage of donation: "<<flush; //Step 13 cin>>percentDonation;//Step 14 cout<<endl<<endl; grossAmount = adultTicketPrice * noOfAdultTicketsSold + childTicketPrice * noOfChildTicketsSold; //Step 15

96. amountDonated = grossAmount * percentDonation / 100; //Step 16 netSaleAmount = grossAmount - amountDonated; //Step 17 //Step 18: Output results cout<<"-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*" <<"-*-*-*-*-*-*-*-*-*-*-*-*-*"<<endl; cout<<setfill('.')<<left<<setw(35)<<"Movie Name: " <<right<<" "<<movieName<<endl; cout<<left<<setw(35)<<"Number of Tickets Sold: " <<setfill(' ')<<right<<setw(10) <<noOfAdultTicketsSold + noOfChildTicketsSold <<endl;

97. cout<<setfill('.')<<left<<setw(35)<<"Gross Amount: " <<setfill(' ')<<right<<" $" <<setw(8)<<grossAmount<<endl; cout<<setfill('.')<<left<<setw(35) <<"Percentage of Gross Amount Donated: " <<setfill(' ')<<right <<setw(9)<<percentDonation<<'%'<<endl; cout<<setfill('.')<<left<<setw(35)<<"Amount Donated: " <<setfill(' ')<<right<<" $" <<setw(8)<<amountDonated<<endl; cout<<setfill('.')<<left<<setw(35)<<"Net Sale: " <<setfill(' ')<<right<<" $" <<setw(8)<<netSaleAmount<<endl; return 0; }

98. Sample Run: (In this sample run, the user input is in red): Enter movie name: Duckey Goes to Mars Enter the price of an adult ticket: 4.50 Enter the price of a child ticket: 3.00 Enter number of adult tickets sold: 800 Enter number of child tickets sold: 1850 Enter the percentage of donation: 10 -*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-* Movie Name:....................... Duckey Goes to Mars Number of Tickets Sold:........... 2650 Gross Amount:..................... $ 9150.00 Percentage of Gross Amount Donated:.. 10.00% Amount Donated:................... $ 915.00 Net Sale:......................... $ 8235.00

99. PROGRAMMING EXAMPLE: STUDENT GRADE Write a program that reads a student ID followed by five test scores. The program should output the student ID, the five test scores, and the average test score. Output the average test score with two decimal places. Assume that the student ID is a character. The data to be read is stored in a file called test.txt, and the file is stored on a floppy disk in drive A:. The output should be stored in a file called testavg.out, and the output file should be stored on the floppy disk in drive A:. Input: A file containing the student ID and five test scores. Output: The student ID, five test scores and the average of the five test scores. The output is to be saved in a file.

100. Problem Analysis and Algorithm Design To find the average of five test scores, first we add the five test scores and then divide the sum by 5. Now, the input data is in the form: student ID followed by five test scores. Therefore, we first read the student ID and then the five test scores. This discussion translates in the following algorithm: 1. Read student ID and the five test score. 2. Output student ID and five test scores. 3. Calculate the average. 4. Output the average. We will output the average test score in the fixed decimal format with two decimal places.

101. Variables: ifstream inFile; //input file stream variable ofstream outFile; //output file stream variable int test1, test2, test3, test4, test5; // variables //to read five test scores double average; //variable to store average //test score char studentId; //variable to store //student ID

102. Main Algorithm 1.Declare the variables. 2.Open the input file. 3.Open the output file. 4.To output the floating-point numbers in a fixed decimal format with a decimal point and trailing zeros, set the manipulators fixed and showpoint. Also, to output the floating-point numbers with two decimal places, set the precision to two decimal places. 5.Read the student ID. 6.Output the student ID. 7.Read the five test scores. 8.Output the five test scores. 9.Find the average test score. 10.Output the average test score. 11.Close the input and output files.

103. //Program to calculate average test score. #include using namespace std; int main() { //Declare variables; Step 1 ifstream inFile; //input file stream variable ofstream outFile; //output file stream variable int test1, test2, test3, test4, test5; double average; char studentId;

104. inFile.open("a:test.txt"); //Step 2 outFile.open("a:testavg.out"); //Step 3 outFile<<fixed<<showpoint;//Step 4 outFile<<setprecision(2);//Step 4 cout<<"Processing data"<<endl; inFile>>studentId;//Step 5 outFile<<"Student ID: "<<studentId <<endl;//Step 6 inFile>>test1>>test2>>test3 >>test4>>test5;//Step 7

105. outFile<<"Test scores: "<<setw(4)<<test1 <<setw(4)<<test2<<setw(4)<<test3 <<setw(4)<<test4 <<setw(4)<<test5<<endl;//Step 8 average = static_cast (test1+test2+test3+ test4+test5)/5.0;//Step 9 outFile<<"Average test score: "<<setw(6) <<average<<endl;//Step 10 inFile.close(); //Step 11 outFile.close();//Step 11 return 0; }

106. Sample Run: Input File: (contents of the file a:test.txt ): T 87 89 65 37 98 Output File: (contents of the file a:testavg.out ) Student ID: T Test scores: 87 89 65 37 98 Average test score: 75.20